1. Field of the Invention
The present invention relates to a method of manufacturing a patterned film by using an aerosol deposition method of forming a film by spraying powder of a raw material toward a substrate.
2. Description of a Related Art
In recent years, with the developments of MEMS (micro electro mechanical systems) related devices, elements such as multilayered ceramics capacitors and piezoelectric actuators have been microfabricated still further and packaged more densely. Accordingly, the manufacture of such elements using film forming technologies has been actively studied.
Recently, an aerosol deposition (AD) method as one of the film forming technologies utilizing the collision and deposition phenomenon of solid particles has received attention. The AD method is a film forming method of injecting an aerosol generated by dispersing fine powder of a raw material from a nozzle toward a substrate and allowing the powder to collide with the substrate or the previously formed film to deposit the raw material on the substrate. Here, the aerosol refers to “a colloid system including a dispersion phase consisting of solid or liquid particles and a dispersion medium consisting of a gas” (written by Kanji Takahashi, “Basis of Aerosol Studies”, Morikita Publishing, 1st edition, p. 1). According to the AD method, dense and strong films with low porosity can be formed, and therefore, the performance of the above-mentioned microelements may be improved.
As a related technology, Japanese Patent Application Publication JP-P2003-142750A discloses a method of forming a piezoelectric actuator having a high-definition piezoelectric material array with a homogeneous thickness. The method of forming a piezoelectric actuator includes the steps of: forming a resist pattern on a substrate; forming a piezoelectric film on the substrate to cover the resist pattern by using a gas deposition method; and patterning the piezoelectric film by removing the resist pattern to fabricate a piezoelectric material array in which piezoelectric material stripes are arranged at predetermined intervals.
Japanese Patent Application Publication JP-P2004-91854A discloses a method of forming a composite structure for forming a brittle material structure, which has an edge portion sharply cut, by using the aerosol deposition method. In the method of forming a composite structure, the brittle material structure, which has brittle material fine particles deposited only on the part of the opening of a mask, is formed by allowing the brittle material fine particles to collide with a base material, onto which the mask has been attached, at a high speed, and further, the mask is removed.
Japanese Patent Application Publication JP-P2004-146750A discloses a method of manufacturing a device unit including a device having a film of a brittle material as a component element on a resin substrate. In the method of manufacturing a device unit, a substrate having hardness DHv2 (dynamic hardness in consideration of plastic deformation) of 40 or more is selected as the resin substrate, an organic film or a metal film having hardness DHv2 less than 40 is patterned on a part where the element is to be formed in the surface of the resin substrate, and then, an aerosol of brittle material fine particles is allowed to collide with the substrate surface containing the organic film or the metal film, and the brittle material fine particles are deformed or crushed due to the impact by the collision so that the fine particles are rebounded, and thus, a brittle material structure is formed only on the organic film surface or the metal film surface within the substrate surface.
Japanese Patent Application Publication JP-P2005-317952A discloses a method of manufacturing a piezoelectric actuator having a piezoelectric material layer formed by spraying a carrier gas containing fine particles of a piezoelectric material on a substrate surface to deposit the fine particles thereon, and the method is for easily forming the piezoelectric material layer on a partial region of the substrate surface. In the method of manufacturing a piezoelectric actuator, a film formation permitting region where fine particles of a piezoelectric material in a carrier gas are deposited to form a film on the substrate surface in advance and a film formation inhibiting region where the deposition of fine particles in the form of a film are inhibited are provided, then, the carrier gas containing the fine particles is sprayed on the substrate surface, and thus, the piezoelectric material layer is formed on the film formation permitting region. Further, in JP-P2005-317952A, the film formation permitting region and the film formation inhibiting region are distinguished by differing hardness, and the ratio between the hardness of the powder and the hardness of the respective regions are disclosed.
By the way, in the case where a patterned film is formed by using the AD method as shown in FIG. 14, a resist mask 903 is formed on a substrate 901 on which an electrode 902 has been formed, a film 904 is formed by spraying an aerosol toward the substrate thereon, and then, the resist mask is removed by wet etching. For example, in the method of forming a piezoelectric actuator disclosed in JP-P2003-142750A, such a method is used. However, when the film is formed by the AD method, the film is formed by the deposition of the raw material powder not only on the opening of the resist pattern but also on the side surface thereof. As a result, in the step of removing the resist, a separation liquid can hardly enters to the resist and the separation of the resist becomes difficult, and thus, the formed patterned film may be damaged.
On the other hand, in JP-P2004-91854A, JP-P2004-146750A, and JP-P2005-317952A, the film formation is selectively performed by partially changing the hardness of the under layer to provide the region (mask part) where the raw material powder can hardly be deposited when the aerosol is sprayed thereon. In this case, the defects that the film is deformed when the mask is removed, that the mask can hardly be removed, and so on are avoidable. However, when the film formation is performed by the AD method, the edge of the mask is scraped and deformed due to the blast effect by the sprayed powder, and the accuracy of the formed film may be reduced.
Furthermore, in JP-P2004-91854A, the mask is formed by attaching a plastic base material, in which an opening has been formed, to a substrate, and thus, it is difficult to cover the microfabrication and high definition of elements.